Penemuan dari dua campuran yang kompleks mengisyaratkan keaneka-ragaman bahan kimia yang bersembunyi di angkasa.
Suatu team riset internasional melakukan riset mendalam terhadap suatu awan yang berupa gas berada di pusat galaksi bima sakti dan mendeteksi adanya etil formate dan n-propyl sianida, dua di antara molekul organik paling kompleks yang pernah di amati di sistem luar matahari. Berdasarkan model komputer dan bukti spectroscopic bagaimana molekul dibentuk, ilmuwan percaya bahwa molekul dengan bahan kimia yang lebih kompleksitas lagi sedang menanti untuk ditemukan di angkasa.
Salah satu dari molekul itu adalah glycine, asam amino yang paling sederhana, yang terhindar dari pendeteksian sampai sekarang. Glycine adalah dua campuran yang memiliki ukuran dan kompleksitas yang sama dan kehadiran nya akan membantu memperkuat kecurigaan bahwa ilmu kimia prebiotik ada di sistem luar matahari kita.
Robin T. Garrod salah seorang anggota riset adalah seorang ahli astrokimia di Cornell University, mengumumkan penemuan pada 21 April 2009 pada waktu European Week of Astronomy & Space Science di University of Hertfordshire, di Inggris. Penelitian ini juga dilaporkan di jurnal Astronomi & Astrofisika (DOI: 10.1051/0004-6361/200811550).
Ulasan penemuan ahli Astrokimia Steven B.B. Charnley dari NASA’s Goddard Space Flight Center, di Greenbelt, Md., seperti yang dikatakan C&EN yang mendeteksi campuran ini membantu melepaskan cahaya baru dan bagaimana molekul yang kompleks dibentuk di angkasa dan ” dorongan untuk masa depan terhadap pencarian asam amino yang lebih tinggi, seperti halnya untuk nucleobases dan tanda heterocyclic mereka .”
Peneliti menggunakan spektroskopi millimeter gelombang panjang untuk mempelajari suatu awan tebal dari gas dan partikel debu yang dingin di daerah formasi bintang Sagittarius B2. Tempat ini di alam semesta telah menjadi suatu harta terpendam yang banyak terdapat molekul organic kecil yang berbeda jenis ( C&En, Juni 16, 2008, halaman 58). Meskipun demikian, mendeteksi etil formate dan n-propyl sianida sulit untuk ilmuwan sebab 36 garis spektrum mereka untuk dua campuran overlap dengan 3700 garis spektrum dari molekul banyak dideteksi orang.
Sumber: http://pubs.acs.org/cen/news/87/i17/8717notw3.html
Molekul Baru di Angkasa
Atraksi Fisika di Udara
Sekumpulan burung Pelikan, Camar dan Angsa terbang indah di udara. Suatu atraksi udara yang sangat menakjubkan! Ada rasa iri yang dapat dimengerti saat manusia menyaksikan pertunjukan ini. Ternyata semua akal budidan kepandaian manusia belum dapat menyaingi kemampuan burung yang dapat terbang dengan mulus dan sempurna tanpa menggunakan alat bantu mesin‐mesin besar yang mengeluarkan suara bising yang memekakkan telingaseperti pesawat‐pesawat ciptaan manusia. Apa rahasianya? Bagaimana burung bisa terbang, mengalahkan semua keterbatasan akibat berat tubuh mereka dan gravitasi bumi? Mereka bahkan selalu terbang sebagai kawanan burung yang dengan kompak menjelajahi udara dengan gerak‐gerik yang indah. Kalah kompakkah manusia? Atraksi terbang burung‐burung di udara ini ternyata melibatkan ilmu fisika. Gerak parasut merupakan gerak jatuh di udara (bisa miring bisa pula vertikal). Sudut miringnya lebih besar dari 450 terhadap garis mendatar. Untuk melakukan gerak parasut, burung rajawali harus memperbesar gaya hambatnya (drag force) caranya adalah dengan memperbesar luas permukaannya (misalnya dengan melebarkan sayapnya).
Ada 4 jenis gaya yang terlibat dalam atraksi udara tertua ini.
1. Drag Force,yaitu gaya hambat udara. Gaya ini berasal dari tumbukan molekul‐molekul udara dengan tubuh burung. Arah gaya ini selalu berlawanan dengan arah gerak burung. Sedangkan besar gaya ini sangattergantung pada luas permukaan burung dan kecepatan burung. Semakin luas permukaan burung semakin besar gaya hambatnya. Semakin cepat burung bergerak semakin besar pula gaya hambatnya ini. Suatu ilustrasi yang dapat menggambarkan drag‐force (hambatan) udara ini adalah hambatan yang dirasakan saat kita berjalan melawan arah angin yang kencang. Hambatan ini semakin terasa besar ketika kita membuka lengan kita lebar‐lebar (memperluas permukaan tubuh kita) atau ketika kita bergerak lebih cepat.
2. Lift Force (gaya angkat) merupakan gaya yang mengangkat burung keatas. Ada 2 hal yang dapat menimbulkan gaya angkat ini: kepakan sayap dan aliran udara yang lewat sayap. Ketika burung mengepakkan sayap kebawah, burung menekan udara ke bawah, akibatnya udara akan menekan balik dan mendorong burung ke atas (hukum aksi‐reaksi). Semakin cepat kepakan sayap, semakin besar gaya keatasnya. Itu sebabnya burung merpati yang hendak terbang akan mengepakan sayapnya secara cepat.Burung yang berat seperti Kori Bustard dari Afrika tentu harus mempunyai otot dada yang kuat sehingga mampu mengepakan sayap lebih cepat untuk mengangkat tubuhnya yang gembrot itu (19 kg).(Karena ototnya keras, daging Kori Bustard keras.... kurang enak dimakan)
Gb.1 aliran udara pada sayap burung.
Pada Gb. 1digambarkan aliran udara ketika melewati sayap. Udara yang mengalir lewat bagian atas sayap akan bergerak lebih cepat karena udara ini harus menempuh lintasan yang lebih jauh. Akibatnya tekanan dibagian ini lebih kecil dibandingkan dengan tekanan udara dibawah sayap. Perbedaan tekanan ini memberikan gaya angkat pada burung. Semakin melengkung (semakin aerodinamis) sayap semakin besar gaya angkatnya.
3. Thrust (gaya dorong) yaitu gaya yang mendorong burung bergerak maju. Gaya ini dihasilkan melalui kepakan sayap yang bergerak seperti angka 8 rebah (dilihat dari samping). Kepakan sayap menghasilkan suatu pusaran udara (vorteks) yang dapat memberikan suatu dorongan bagi burung untuk bergerak maju di udara. Besar‐kecilnya gaya dorong ini sangat tergantung pada kekuatan otot terbang.
4. Weight (gaya berat) yaitu gaya tarik gravitasi bumi. Besarnya sangat tergantung pada massa burung. Arahnya vertikal ke bawah.
Gambar2 Gaya‐gaya pada burung yang sedang terbang Kombinasi ke 4 gaya ini dimanfaatkan burung untuk melakukan berbagai atraksi seperti parachutting (gerak parasut), gliding (meluncur), flight (terbang ke depan), dan soaring (membubung) (pintar yach burung‐burung ini....)
Parachuting (gerak parasut)
Gliding (meluncur) yaitu gerak jatuh yang membentuk sudut lebih kecil dari 45°dengan garis mendatar. Fokus utama dalam gliding adalah meluncur semendatar mungkin. Ini dilakukan dengan memperkecil gaya hambat udara. Dalam melakukan gliding burung Fulmar dapat menempuh jarak mendatar 8,5 meter tetapi hanya turun 1 meter saja. Burung pemakan bangkai (Vultures) lebih bagus lagi, burung ini dapat menempuh jarak mendatar 22 jarak meter dengan turun hanya 1 meter.
5. Flight (terbang)
Gerakan flight (terbang) dilakukan dengan mengepakkan sayap. Kepakansayap digunakan untuk menghasilkan gaya dorong ke depan (thrust) dan gaya angkat (lift). Gaya dorong dan gaya angkat ini dapat diatur oleh burung untukmengendalikan arah, kecepatan, dan ketinggiannya (ternyata otak burung cukup cerdas untuk menghitung fisika he...he..he.....).Ketika burung hantu turun dengan kecepatan tinggi untuk menangkap tikus, burung hantu mengecilkan drag force dengan merampingkan tubuhnya atau menekuk sayapnya. Ketika sudah dekat dengan mangsanya (akan mendarat), burung hantu memperlambat gerakannya dengan memperbesar dragforce yaitu dengan mengembangkan sayapnya (wuiii ...hebat sekali ilmu fisika burung hantu ini...)
Soaring (gerak membubung)
Gerak membubung merupakan gerak naik tanpa mengepakkan sayap. Gerakan ini dapat dilakukan dengan memanfaatkan arus udara. Akibat pemanasan matahari suhu udara yang dekat permukaan bumi menjadi lebih panas, udara panas ini akan naik ke atas dan menimbulkan arus udara ke atas. Arus udara inilah yang dimanfaatkan oleh burung rajawali untuk membubung tinggi tanpa perlu mengepakan sayapnya yang besar (hemat energi lho...). Burung camar atau burung albatros, lain lagi. Untuk membubung, burung camar memanfaatkan arus udara yang dipantulkan oleh permukaan air laut. Itu sebabnya burung camar selalu berada dekat‐dekat dengan permukaan laut.
Parade Burung Terbang
Pernah lihat angsa atau burung terbang bermigrasi (berpindah tempat)? Angsa ini umumnya terbang berkelompok membentuk suatu parade yang sangat indah, jarang ditemukan angsa terbang jauh sendirian. Selain untuk meningkatkan keamanan terhadap serangan predator, kebersamaan itu juga mengurangi resiko tersesat di jalan saat melakukan migrasi jarak jauh. Dalam melakukan migrasi dari satu tempat ke tempat lain angsa‐angsa ini memanfaatkan medan magnetik bumi sebagai penunjuk arah.
Dalam melakukan parade, angsa‐angsa ini seringkali membentuk formasi seperti huruf V (gambar 3). Angsa yang paling depan (pemimpin) merupakan pembuka jalan yang harus bekerja keras “memecah” hambatan udara, sehingga angsa dibelakangnya dapat bergerak lebih mudah. Ketika pemimpin ini lelah, temannya segera menggantikan posisinya (wah ternyata angsa tidak egois ...nggak mau enak sendiri). Dalam formasi huruf V ini gerakan angsa‐angsa dalam kawanan ini sangat sinergi sehingga mereka tidak perlu keluar tenaga terlalu besar (pemakaian energi lebih efisien) untuk melakukan perjalanan yang jauh (wah tampaknya kita harus belajar dari angsa dalam bekerja sama...).
Angsa‐angsa ini tampak kompak sekali, seakan‐akan tidak pernah ada yang salah arah. Sebenarnya berbagai kesalahan arah terbang tetap terjadi, hanya saja kesalahan itu dapat dengan cepat dileburkan sehingga tidak terlihat mempengaruhi arah terbang kawanan. Pada gambar 4, sekumpulan angsa sedang bergerak ke arah utara. Jika satu angsa menyimpang dari posisi (1) keposisi (2) lalu ke posisi (3) dan (4), maka angsa‐angsa lain akan berusaha menyesuaikan diri (dengan memperhatikan aliran udara dan kondisi udara di sekitarnya) sedemikian sehingga terjadi perubahan posisi tetapi arah gerak kawanan tetap tidak berubah yaitu tetap ke arah utara. Eh tahu nggak... konsep perubahan posisi ini dapat diterapkan dalam ilmu manajemen modern lho.
Menurut konsep ini jika ada seorang mempunyai ide yang dapat menyimpangkan arah perusahaan tetapi menguntungkan perusahaan itu, orang ini tidak akan dikucilkan. Teman‐temannya yang akan menyesuaikan diri sedemikian sehingga misi dan visi perusahaan tetap tidak berubah, walaupun mungkin posisi teman‐temannya itu bisa berubah (wah keren... belajar dari angsa).
Memang asyik mengamati gerakan‐gerakan burung. Ternyata dalam ilmufisika kita harus banyak belajar dari burung. Begitu indah dan mempesonanya atraksi fisika yang mereka pertontonkan di udara selama jutaan tahun sehingga rasanya kita ini tidak ada apa‐apanya.
(Yohanes Surya).
Discovery of Earth-mass Planet Looms
The discovery of the lightest exoplanet ever found, less than twice the mass of the Earth, has electrified a week-long meeting on astronomy and space science in Europe.
The stunning finding was made by a team headed by Michel Mayor of the Geneva Observatory. The icing on the cake is a related discovery that a previously discovered "super-Earth" orbiting the same star appears to reside in the habitable zone.
The finding portends the discovery of a true Earth-mass planet, which could come in about two years, Mayor said.
Mayor made the very first discovery of an exoplanet, a Jupiter-sized world that orbits the star 51 Pegasi, in 1994. Among his many planet discoveries since then at ESO's La Silla Observatory in Chile, Mayor has made a specialty of observing the star Gliese 581. Located 20.5 light-years away in the constellation Libra ("the Scales"), Gliese 581 is a red dwarf star with only one-third of the mass of our sun.
Two years ago, Mayor discovered a planet the size of Neptune and two super-Earths orbiting this star. The newly discovered planet, named Gliese 581 e, is now the fourth known planet in this solar system and the lightest, weighing in at only 1.94 Earth masses. It flies round the star at dizzying speed, taking just 3.15 days to complete an orbit. "The surprise for me was to discover a planet with by far the lowest mass seen to date," says Mayor.
This new planet orbits so close to the star that its water would have boiled away long ago. It is therefore not in the habitable zone – the region of a solar system where water can stay liquid on the surface of a rocky planet, and, consequently, where scientists expect life can occur. In our solar system, the habitable zone is roughly between the orbits of Venus and Mars (with Earth sitting not quite in the middle).
In finding the new planet, Mayor has been able to more accurately determine the orbit for the outermost planet, Gliese 581 d. One of the super-Earths in the solar system, this planet is closer to the host star than was thought when it was discovered in 2007. And that provided the second great surprise. "It is the only (Earth-like) exoplanet found inside the habitable water zone of the parent star," says Mayor.
Gliese 581 d is 7 Earth-masses, and team member Stephane Udry says the planet is probably too massive to be made only of rocky material. "We can speculate that it is an icy planet that has migrated closer to the star," he says. At the European meeting, Mayor added the latest news indicated, "No icebergs, but there may be an ocean at the surface, meaning this is a new class of ocean planet."
To detect exoplanets, Mayor's team studies a star's radial velocity, in which the tiny tugs exerted by orbiting exoplanets produce a complex wobble in the star. This wobble can be analyzed to learn about properties of the planets in the solar system. The velocity of a star with multiple planets has to be followed for several years to discover the different properties of its orbiting planets, and this requires instrumentation that is extremely stable from year to year -- one of the big challenges in detecting exoplanets through the radial velocity technique.
The team's observing program began back in 2004 with a sample of 400 sun-like stars.
Mayor is now scooping up small exoplanets that have been missed by a rival search technique (called transit photometry) which involves measuring the tiny fall in a star's magnitude when an exoplanet passes between the star and the Earth. Both techniques, transit photometry and radial velocity, are strongly biased to catch giant planets with the mass of Jupiter or more, as well as smaller planets that orbit very close to their star. But to find small planets orbiting within a star's habitable zone, Mayor's approach now seems to have the edge.
The team has found that one-third (30%) of exoplanet systems discovered to date include small bodies. "We have discovered a new category of small exoplanets," says Mayor. "Within a couple of years we will drive down our lower limit of detection to the mass of the Earth. The next challenge after that is to detect a twin of the Earth in the habitable zone of a solar-type star."
The next stage for Mayor's team is to migrate the detection technology from the current 3.6-meter telescope to ESO's 8-meter Very Large Telescope in order to improve the precision of observations. After that, Mayor looks forward to using the European Extremely Large Telescope (E-ELT), a 42-meter eye-on-the-sky that is planned to be operating by 2018.
Currently in the later stages of design, this facility will be capable of directly imaging larger exoplanets, and possibly will be able to search their atmospheres for biosignatures. E-ELT will answer fundamental questions on the formation and evolution of exoplanets, bringing us one step closer to answering the question: are we alone?
By Simon Mitton
What Is Dark Energy?
Dark energy is the name given to an unexplained force that is drawing galaxies away from each other, against the pull of gravity, at an accelerated pace.
Dark energy is a bit like anti-gravity. Where gravity pulls things together at the more local level, dark energy tugs them apart on the grander scale.
Its existence isn't proven, but dark energy is many scientists' best guess to explain the confusing observation that the universe's expansion is speeding up. Experts still don't know what's driving this force, but the quest to learn more about dark energy is one of cosmologists' top priorities.
Confounding expectations
The story of how dark energy was discovered is a classic case of science confounding expectations.
In the mid-1990s, astronomers set out to measure how fast the universe was expanding. Because gravity draws mass together, most experts expected to find that gravity had slowed down the universe's rate of ballooning, or perhaps that the rate was staying about the same.
Instead, it appeared that the expansion was doing neither: It was speeding up.
"The data wasn't behaving as we thought it would. There was a lot of nervous laughter," said Brian Schmidt of the Australian National University in Canberra, who led a team along with Johns Hopkins University astrophysicist Adam Riess that helped discover dark energy in 1998.
The evidence was based on measurements of bright exploding stars, called supernovae, that astronomers were using as lampposts to track distance. By looking farther away, scientists are able to peer back in time, since the light from distant objects has taken billions of years to reach us.
The scientists observed many supernovae at different distances to determine how fast they are speeding away from us. (They measured the objects' red-shift, or how much their light had been changed due to the Doppler effect, which is the compression or expansion of waves that occurs when an object is moving toward or away from you. An analogy is the siren of an ambulance that changes pitch as it moves toward you, then passes you and heads the other way — its waves are first compressed, then stretched.) These measurements gave astronomers a picture of how fast the universe was expanding at different points in its history.
Shocking results
The researchers also found that the universe is expanding faster today than at any time in the past.
"At first we were reluctant to believe our result," said Saul Perlmutter, an astrophysicist at the Lawrence Berkeley Laboratory of the University of California, Berkeley, who led a competing team that found the same results as Schmidt and Riess. "But the more we analyzed it, the more it wouldn't go away."
To explain these puzzling findings, some scientists have revived an old idea of Einstein's that had been discarded as false: that the vacuum of space has energy in it that acts repulsively and accelerates the expansion of the universe. Einstein called this idea the cosmological constant, and referred to it as his "biggest blunder."
Now the cosmological constant is one of the leading theories of why the universe is blowing up like a balloon at ever-increasing speed.
Dark matter
Dark energy is sometimes confused with the similarly mysterious dark matter, though the two are separate entities.
Dark matter is a hypothesized form of matter that doesn't interact with light, so it is invisible. Astronomers deduced its presence by noting its gravitational pull on stars in galaxies.
Taken together, dark matter and dark energy seem to make up most of the mass of the universe (matter and energy are considered to be two forms of the same thing, thanks to Einstein's famous equation E=Mc^2). Dark energy is thought to account for 74 percent of the universe, while dark matter adds about 22 percent, and normal, visible matter contributes a puny 4 percent.
As if the discovery of dark energy weren't bizarre enough, it has stirred up a whole host other issues. For example, dark energy adds fuel to the fire of believers in multiple universes, or the idea that our own existence is just one of countless worlds in which the constants and conditions are different. There might be other universes in which dark energy doesn't exist, and the universe does slow in its expansion, cosmologists say. Maybe that's why our universe is so peculiar.
By Clara Moskowitz
Newfound Spiral Galaxies Oddly Young
Astronomers have discovered an unexpected cache of spiral galaxies that appear to have formed recently, long after the period early in the history of the universe that most galaxies were thought to have been created.
These younger galaxies are big and bright, like our own Milky Way. The reigning hypothesis of galaxy formation holds that such well-established spirals would have formed about 13 billion years ago, shortly after the Big Bang.
But the new discovery of a group of 15 spirals that look to be much younger may upset that thinking.
Though they are just as luminous and large as normal spirals, these galaxies appear to have all the hallmarks of youth. They don't have nearly as many heavy elements, called metals, as would be expected for older galaxies. All elements heavier than helium are created through nuclear reactions inside stars, and elements heavier than iron are made when stars die in supernovae. Thus, the longer a galaxy has been alive and forming stars, the longer its stars have been churning out heavy metals, so the greater abundance you would expect.
But the chemical abundances of the newly discovered galaxies would suggest they are only about 3 billion or 4 billion years old.
"We're not saying there's a complete breakdown in the theory of galaxy evolution, but that these objects do run counter to the standard model," said Indiana University astronomer John Salzer, the lead author of a paper detailing the study in the April 10 issue of the Astrophysical Journal Letters. "These potentially could have formed much more recently. The significance is that they give us the opportunity to study galaxy formation and evolutionary processes which would otherwise be veiled at the vast distances involved in looking at things at these early stages of the universe."
If this age estimate proves to be correct, these galaxies could present an unprecedented opportunity to study massive spirals at a younger point in their evolution, and at closer range, than is generally possible.
"These objects may represent a unique window on the process of galaxy formation, allowing us to study relatively nearby systems that are undergoing a phase in their evolution that is analogous to the types of events that, for most galaxies, typically occurred much earlier in the history of the universe," Salzer said. Another possible explanation for the unusual galaxies is that they are the product of collisions between two smaller galaxies. This could explain why they have low levels of metals, since dwarf galaxies tend to have few heavy elements to begin with. Also, the chaos of a collision can stimulate a burst of star formation, which might explain why the galaxies appear so bright. However, this scenario would require the galaxies' luminosity to multiply by about 30 times after merging — a boost much greater than is usually seen.
"It's just hard for me to fathom, and hard for models to account for, an increase by a factor of 30," Salzer told SPACE.com.
Salzer discovered the galaxies through the Kitt Peak National Observatory International Spectroscopic Survey (KISS), a multi-year project to observe more than 2,400 star-forming galaxies. He and his team have requested time on the Hubble Space Telescope to try to distinguish between the two possible explanations by hunting for evidence that the galaxies have undergone collisions.
By Clara Moskowitz
